The present invention relates to molded plastic wheels and, in particular, to a light duty utility wheel such as used with trash containers, barbecues, lawn mowers, utility carts, etc.
A variety of utility wheels have been developed over the years for numerous light and medium duty applications. Inherent to the structural rigidity and durability of any wheel is the necessity of a secure attachment between the wheel and a supporting axle. Depending upon the loading and application, varieties of attachment mechanisms can be employed to retain the wheel to the axle. The simplicity or complexity of the attachment mechanism can affect the overall apparatus cost.
Utility wheels of the present type are commonly mounted to a supporting axle with the benefit of a spring biased pin. For many wheels, it has been necessary to insert mold or stake mount one or more pin containing retainers into the wheel, such that with subsequent mounting of the wheel, a spring biased pin is captured within an axle groove. Examples of spring biased pin retainer assemblies can be seen at U.S. Pat. Nos. 277,425; 390,465; 575,649; and 2,568,834.
End cap retainers, commonly referred to as pal nuts, having flexible fingers are also known and can be mounted over the exposed end of an axle to prevent wheel release. The fingers of a cap piece typically flex to frictionally engage the axle or a groove formed into the axle, for example, see U.S. Pat. No. 2,615,759.
A cotter pin and one or more washers may also be mounted to the axle to retain the wheel to the axle.
U.S. Pat. Nos. 4,544,425 and 5,143,427 disclose bushings which can be separately mounted between a wheel and axle to provide a bearing surface and secure the wheel to the axle. The former patent includes a bushing containing a number of flexible fingers which mount into annular recesses at the axle. The latter patent discloses a bushing having end pieces which expand upon the insertion of the axle to simultaneously grip the axle and expand to grip a mating wheel surface.
Nowhere are wheels known having integrally formed members that flex to mate with the axle to retain the axle to the wheel.
In appreciation of the foregoing deficiencies, the presently improved wheel was developed to convert a normal molding inconvenience into a wheel of improved construction. The improved wheel securely mounts to available axles to provide a durable attachment with reduced assembly time and without component complexity.
The stability and loading characteristics of the wheel are also enhanced through a number of internal trusses that span the tread to sidewall transition. The trusses are formed intermediate external traction lugs that project from the tread surface.